Why does onions grow bigger from seeds than sets?

There's no good reason why your onion sets aren't performing if you are giving them what they need.

First of all the soil needs to be slightly acid with a ph of between 6 and 7. Personally, I don't even check the ph in my plot. I apply lime in my normal scheme of rotation with my brassica crop. I follow brassicas with spuds which get a goodly amount of fym and a handful of growmore or similar per yard. I follow the spuds with my onions which again get a goodly amount of fym and growmore or similar.


I'm not going to knock the guy who cuts back the foliage on his onions. If it works for him then well done him but I would neverdo it because it works for me without doing it.

As for seed or set. Yes, there will be less problems with bolting but I only really have a problem with red onions bolting. The others are ok with me. As for size, for me, that depends on variety only. not on growing from seed or set.


A wee further word on onions from sets bolting. A set is an immature onion which has its growth stopped prematurely and is then replanted the following year. Onions are biennials and will normally grow to be a bulbin the first yearand then bolt in the second year. Harvesting immature onions prematurely seems to disturb the normal second year boltingand the onions will hopefully grow into decent bulbs but they can bolt and this can be affected by weather conditions. Using heat treated sets can help eliminate bolting. Over a period of time the sets are exposed to heat which destroys the flower embryo within the set meaning it can't throw a flower head.

Hope all of that helps.

I think the onions size is a lot to do with variety and seed/bulb starting times.

from my experience of growing from seed so far... the smaller onions from sets would totally be worth it - at least I'd have onions!

last year all my onions , sets and seeds, only grew enough to make very average sized pickled onions as we had a summer without heat or sunshine, the worst I can recall ever and I am in my 60s, so fingers crossed for this year...

All the onions I'm growing this year are coming from seed .
I find them to be far more superior to sets .
1. White onion queen
2. Mammoth onion
Both doing really well

My opinion is that with all onions its down to cultivar and growing conditions.

I like red onions and because of the problem of bolting I use heat treated sets, on order from last year they have yet to arrive. I know they will be smaller than white onions but except that because the taste suits my palette.

With AP's help I grew some white onions from seed, the largest was just short of 4 pounds.